Hypodermic injector



A. vENDlT-ry v 2,762,370 HYPODERMIC INJEcToR 2 Shee'ts-Sheet 1 sept. 11,1956 Filed Sept. 7, 1954 Sept 11, 195-6 A. vENDlTTY Y 2,762,370

HYPODERMIC INJECTOR Filed Sept. '7, 1954 2 Sheets-Sheet 2 INVENTOR.

@B2i/why Vendi/[y HYPODERMIC hameren Anthony Venditty, Detroit, Mich.,assi'gnor to The R. P. 'Scherer Corporation, Detroit, Mich., acorporation of Michigan Application September 7, 1954, SerialNo.74545`4'47 6 Claims. (Qi. 12e-F173) vThis invention relates to animproved needleless-hypcidermic injector of the type shown and describedin the dpending application of R. P. Scherer, Serial-No. 170,101, .filedJune 24, 1950. Instruments of this kind are adapted to discharge -liquidmedicament from an orifced ample in the form of a minute stream or jetat two diiferen'tpressure stages sequentially. The initial high pressuredischarge causes the jet stream to distend the skin and force 'theliquid to a predetermined depth beneath the su'rfaee, depending upon`the magnitude of the pressure. AAfter the minute opening in theepidermis has been produced the .pressure of the `stream is immediatelyreduced toa lower second stage for completing transfer of the remain'-ing-liquid from the ampule.

Y The instrument shown and described in the application above referredto employs five coil springs as' a soure of p ower for driving a dualplunger assembly comprising a .primary plunger 4of small diameterslidably mounted V'With'- inV a secondary plunger having a diameterequal "to lthat of the exible follower or stopper within' the bore ofthe ampule. The follower is cup-shaped and is adapted to expel-liquidthrough the minute orifice in the `end of the ampule as -it is vadvanceddown the bore :by the plunger. As the power springs expand, the primaryplunger exerts a force against the central portion o'f the bottom of thefollower to distend that portion a short distance and simultaneously'eject a small amount of liquid from the' orifice the ampuleunder highpressure. The magnitude of this pressure during the iirst stagedetermines the depth gaf-penetration -of the jet stream below. thesurface. After the primary plunger-hastravelled to the fend of 'itsstroke', which yis Yrelatively short, the secondary plunger IVengagesthe entire area of the bottom of the follower and moves the followerdown the bore of the ampule to compiete theinjection at reducedpressure.' The reduction in pressure, ofcourse, -is due to the increasein the area engaged jby the plunger. The pressure during the secondstage is ljust suiiicient to f e'ed the liquid through the channelformed during the first pressure stage.

`It has been found that the coil springs employed .inthe injectorconstruction .just described cause the liquid to lbe expelled in surgesrather than at substantially uniform pressures.Y Some patients find such surges to be a source of p ain. The amount of deviation from thedesired .pressure i s not great, but the fluctuations occur veryrapidly. Indications are that these undesirable rapid fluctuationspressureare tied in with the natural frequencies `of the springs.Y VCoil` springs made from braided wire and having alow natural frequencyhave beenfound to reduce the-surge to a minimum with substantiallycomplete climi'- natien of pain to the patient due to rapidlyvfluctuatii'ig pressure. However, springs of braided construction 'areexpensive and increase substantially the cost of the instrument. I nowhave found that thev undesirable frequencies which apparently areresponsible for the rapid surges in pressure may be sufficientlyminimized vor dampened by employing pairs of coil springs havingdifferent natural frequencies. By matching dissimilar frequencies,thevibrations causing the pressure deviations may be dampened orcanc`elled out. In the construction Iof the instrument in accordancewith this invention, therefore, power springs are used in pairs; thetotal number may range from 6 to l2.

Ahothe'robjectof this invention is to provide aninstrument of the typeVdescribed which is more economical to l.produce vthan those madepreviously, this object being accomplished by greatly simplifying theconstruction of the power release mechanism, and thrust bearing betweenthe latch housing and the body. l

A further object is the provision of av novel dual plunger assembly inwhich the primary plunger is iii'ted to (the power :means land isadjustable with respet to A the fol- 7lower in the ampule.By'adjust'in'g the distance between the primary plunger 'and thefollower, the impact force with whichithe plunger strikes the followermayibevaried, and vthis "in turn results in variation 'in the pressureatwhich the lliquid is "ejected from' the oric'e inthe ampule. in'prioriinstrumen'ts capable of injeoting at two 'pressure `stages Ano:p'ryision was-made for 'varying the impact of `primary plunger. l y

Another object is the' provision of a primary plunger which is axiallyadjustable with respect to the ampulenf'ollower by rotating thefast-lead lifting Esciew in thepower mechanism, r`but which is 'ot ingaitialengag'ment with Said screw. Bi li'finatiagaxial engagement bei'plunger andthe fast-lead lifting screw; their u1 on' the threads ofthescrew, due to liquid`res1str n the ampule, and the 'friction attendantthereto, Ais e yininatlefd. These and other objects of the inventionwill appear as' the follo'xving description proceeds.

In the'drawing: l n A Figure l is a longitudinal oross-seetional.through the inst-rumentconstructed in acordanee with the invention; l Y

Figure 2 is a sectional Vview taken along the line 2-'Z `ofliigurel; v ly y. Figure 3 is an elevational view of the mating heads employed forrotationally engaging the screw and the .privmary plunger for adjustmentof the latter with respect to the` ampule follower; Y A l l l l Figure'4 is a sectional view `of Vthe upper end ofI the instrument Vshowingthe latch wedges in Vretracted position; Figure 5 is a sectional Viewalong the line 5'-5 of Fig'- urel;and I Figure 6 is a longitudinalcross-sectional View of the lower end of the instrument after the nuthas engaged the secondary plunger. H

The invention lies in the construction and arrangement of the variouselements comprising the injector, particularly the novel latch mechanismand the duel plunger assembly. l Y, ,l y Reference is now made to Figurel of the 'drawings in which vthe numeral 10 designates an elongated bodyhousing most of the mechanism of theinjector. Ay dosage sleeve 12 isscrewed onto the threaded lower lor ampule-containing end of theinjector and a winding sleeve 14 is rotatable on the upper end thereof.The sleeve 14 has an inturned flange 16 coacting with an annular ring orridge 18 on the body 1,0 to prevent longi tudinal movement in onedirectionrelative to the body. A combination latch housing and upperbearing sup"n port 2d is screwed into the upper end of the `*windingsleeve i4 with a thrust bearing 22 interposed between the body and thelatch housing. Arelease button cap 24, which may be molded from a'suitable thermoplastic resin', is assembled with the latch housing 20,being held in place by a conventional non-reversible bayonet con#nection. The entire assembly of the winding sleeve 14, latch housing 20and the cap 24, is adapted. to rotate as a unit since the sleeve 14 andthe housing 2l)v vare locked together by a key 25 which lits intomatching slots 19, as best shown in Figure l.

The dosage sleeve 12 has threaded on its lower end an ampule holder 4dadapted to receive an ampule 42 containing medicament 44 and having aexible cup-like follower 46 in the upper end thereof. The ampule ispierced with a minute orifice 4S in the lower end thereof. The ampulefollower 46 may be made from a resilient plastic material or rubber,preferably an oil resistant rubber such as polychloroprene, Buna N, orthe like. Other rubber parts employed in the construction of thisinstrument should likewise preferably be made from similar oil-resistantstocks.

The dosage sleeve 12 is locked against rotation by means of a latch 15which tits into grooves 17`spaced circumferentially about the insidesurface of the sleeve. By rotating the sleeve 12 liquid medicament 44may be predischarged The sleeve may be marked externally to indicate theexact volume predischarged when the sleeve is rotated through the arcdened by the successive. grooves 17. This feature is conventional.

The internal mechanism of the instrument includes a Vnovel plungerassembly consisting of a primary plunger 50 having an externallythreaded upper end 51 screwed into the nut 70, and a secondary plunger60 in which the primary plunger 50 is slidably mounted. The threads 57on the upper end 51 of the plunger 50 are single ,threads asdistinguished from double threads which are .employed within thesleeve-like portion of the nut 70 for purposes to be explainedpresently. The lower end 62 of the secondary plunger 64) is adapted toslide within the ampule 42 to advance the follower 46, while the lowerend of the primary plunger 50 is adapted t0 bear against the centralportion only of the top of the follower 46. The upper portion of thesecondary plunger 60 terminates in an integral circular head 64 adaptedto slide axially within the sleeve 12, its upward stroke being limitedby the lower end 11 of the body 1t). A washer 66 made from rubberymaterial is seated in a counterbore in the top surface of the head 6l)to dampen vibrations that might be transmitted through the secondaryplunger 60 from the nut 70. A similar rubber-like washer 68 is adheredto the bottom of the sleeve 12 to cushion the ,blow of the head 64 whenthe instrument is operated without the ampule in place. Washer 66further serves this purpose.

The means for propelling the primary plunger S comprises coil springs86, 81 inserted in 'blind axially-extending openings 13 spacedcircumferentially within the body 10. Single springs may be employed ineach opening 13, but preferably, l use springs in pairs as shown inFigures l and 5, internal spring 81 being of smaller diameter and ofopposite helix to external spring 80. Each pair of springs indiametrically opposite openings 13 must generate equal total force toprevent the tend- .ency to cock. It is preferred that the springs in thesame opening and in adjacent openings be of different naturalfrequencies, which tends to cancel out vibrations that result in rapidfluctuations in the pressure of liquid 44 expelled from the ampule.Springs 80 (or springs 81) in diametrically opposite openings need notbe of the same natural frequency.

The bottom surfaces of the springs seat in recesses 71 in the surface ofthe nut 70, and concentric with the openings 13. The tops of the springsseat against the body 10. Pins 71a, fixed at their lower ends to the nut70, extend upwardly within the openings 13 along the axes thereof andserve to prevent the springs from buckling.

The nut 70 has a long sleeve-like extension 72 projecting upwardly intoa central bore 73 in the body 10, and is keyed thereto as indicated at72a (Figure 5) to prevent rotation. The sleeve 72 is internally threadedwith two styles of threads. Approximately the lower onequarter hassingle threads and the remaining upper portion has double threads. Alifting screw 74 is adapted to. turn within the sleeve 72 for liftingthe nut 70 to compress the springs 80, 81 seated therein. The screw 74has double threads 75 to match those in the upper portion of the sleeve72. Thus, one revolution of ro tation within the sleeve 72 will causethe screw 74 to travel twice the distance of the single threaded primaryplunger 50 when the latter is rotated one revolution within the lowerend of thev sleeve 72. The screw 74 serves the dual purpose of liftingthe nut 70 to compress the springs and of adjusting the primary plungerSi) to a certain predetermined position with respect to the follower 46by rotating the plunger to move it along its threads 57. Y

To prevent a tendency of the screw '74 to spin back due to the reactiveforce of the follower 46, and thus eliminate friction or torque loadbetween the threads of the screw and the sleeve 72, axial engagement ofthe end of the screw vand the primary plunger is avoided in the presentconstruction. Adjustment of the primary plunger 50 by rotation of thescrew without axial engagement is possible because of a special couplingarrangement best shown in Figure 3. Screw 74 carries a head 53 integraltherewith and primary plunger 50 carries a complementary head 52 on theend of shaft 54 which is swaged into opening 55 in the end of theplunger 50 and held therein by serrations 56. Vertical faces 52a and 53aare adapted to engage so that primary plunger 50 rotates with the screw74. Since the threads 75 are double and the threads 57 are single thescrew travels twice the distance of the plunger and the coupling heads52 and 53 will separate and disengage within two revolutions. The endfaces 521: and 53h of the heads may -abut when the screw is movingtoward the plunger due to the fast lead of the screw threads 75. Toavoid jamming, the faces 52h and 53b are bevelled at an angle equal toor greater than the pitch of the screw threads 75.. By this arrangementthe heads 52 and 53 engage so that the primary plunger may be adjustedwith respect to the follower without moving the secondary plunger 60.The latch mechanism for locking the screw 74 against axial movement bythe springs until such time as it is released by pressing button is bestshown in Figures l, 2 and 4. A pin 76 extending through the upper end ofthe screw 74 is adapted to slide axially within slots 77 providedtherefor within the latch housing 20. Latch wedges 82 project throughthe openings 83 provided thereforwithin the latch housing 20. The outerends of the wedges 82 are cut out to embrace thesurface of the screw 74while the upper surfaces contain grooves 86, which embrace the ends ofthe pin 76 when the screw is in locked position, as shown in Figure 1.The latch wedges 82 are tapered toward the inner ends, the slope of thetaper preferably being about 20 from horizontal. The cupshaped button 90is provided with an inwardly turned flange 93 adapted to bear againstthe outer ends of the latch wedges 82 normally to prevent them fromretracting into the grooves 84 in the latch housing. Button 90 may bedepressed, causing the side walls thereof to move downwardly into thegrooves 84 against the compression of the spring 85, whereupon grooves92 in the side wall of the button become aligned with the latch wedges82. Because Vof the slope on the bottom of the wedges 82, they moveoutwardly into the groove 92 under the inuence of the springs. 80, 81,which are tending to thrust the screw 74 downwardly, whereupon the screw74 is released.

The inside edge 95 of the inturned flange 93 on the button is tapered tocontrol button pressure. An'angle Aof' about 4 or 5 is enough to preventthe button from freezing due to thrust on wedges 82 from the screwpressure'. The button pressure may be controlled by changing this angle.

To keep the button 90 depressed While the wedges 82 are in the slot 92,a pair of small opposed bosses 91 are provided on the inner surface ofthe button cap' 24. By

essaiera .igrevenangfthe hun@ aanmaning' up @tannin-straatnaation .duetoithe friction of the bosses' thewedgeszrejn In operation, the windingsleeve1`4is rotat'ed'counter clockwise to turn the screw 74`out'of-thesleeve'72'pe'p`ara'- tory to compressing the springs 8 0 and 8 1. .(Itis assumed that the Vinstrument at this point has just been dischargedand the plunger assembly-fis in the lower position within the dosagesleeve 12.) As the pointed-end .74a of the screw 74 contacts andcompresses 'therspring 85,'the button moves upwardly and forces thewedges out of the slot 92 and underneath the pin 76 to latch the screw74. The spring 85 then snaps the button to its normally raised position.The winding sleeve 14 is then rotated in a clockwise direction to turnthe screw 74 within the sleeve 72 and lift the nut 70 to compress thesprings 80, 81.

As the nut 70 moves up the threads of the screw 74 the head 52 fixed tothe plunger 50 engages the head 53 on the lower end of the screw and themating faces 52a and 53a slide into rotational engagement. If the button90 is depressed when the springs are fully compressed, the maximum depthof penetration of the jet .stream discharged from the ampule 42 willresult because the impact of the primary plunger 59 on the follower 46is greatest. The magnitude and duration of the rst stage pressure isdetermined by two factors: (l) the distance between the end of theplunger 50 and the follower 46, which determines the amount of impact,and (2) the distance the primary plunger 50 moves into the ampule beyondthe end of the secondary plunger 60. In the present constructiondistance (l) is variable and distance (2) is constant. To reduce thepressure of the first stage of the injection the winding sleeve 14 maybe backed off, that is, rotated in a counterclockwise direction, todecrease the distance betwen the end of the plunger 50 and the follower.This causes the nut 70 to be lowered, but due to the style of screwthreads 75 and 57, the plunger 50 descends at half the rate of the nut70. Therefore, if the nut 70 descends .10 inch, the plunger 50 descendsonly .05 inch. By adjusting the rotation of the winding sleeve in acounterclockwise direction the distance between the primary plunger 50and the follower 46 may be reduced from the maximum to any distance downto zero, at which point the plunger and the follower are engaged andthere is no impact at all. This arrangement makes possible very accuratecontrol of the pressure during the first stage of the injection, sincethe plunger 50 moves only a small distance per unit rotation of thewinding sleeve 14. Complementary graduations on the winding sleeve andthe body may be provided to designate to the physician using theinstrument the magnitude of the initial stage pressure, just as in priorinstruments.

A new ampule is then fitted into the nose of the instrument and securedin place by means of the screw cap 40. To discharge the medicament thebutton 90 .is depressed, causing the wedges 82 to slide into the slot 92provided therefor, which releases the screw 74, permitting the springsthe propel the nut downwardly at a rapid rate. Primary plunger 50strikes the follower 46 with a force determined by the impact distance,turns the follower inside out and pushes it down into the bore of theampule to the point indicated in Figure 6. At this point the nut 70engages the secondary plunger 60 as it travels downwardly causing theremaining liquid in the ampule to be expelled at reduced pressure.

It has been found that the combination of springs 80 ,naar uses-nana'in-aanstaan 'tss-passera@ led `vto lo'neen'f'l thereof and `adapted toyhold anori through thejoriil'ce, powerfrnfefah Jplunger includingcoilsprings moutitedcficentric'ally in uenc'ies, or at least minimizes thante Itnt: -exteatwhat injection is virtually painless;

Various modifications vinthe structuref theginsftrufnitt will occur tothose vskilled inthe art without departing inl-the body cancels out *theobjectionable high fed `fromfthe spirit and scope of the invention. -It=s, VVforeynot my intention to limit the inventiontotheiformlsillustrated 'other 'than as necessitated v"by -the scope "of theappended claims.

l claim as my invntio'n 1. In a hypodermic injector, an 4assetrtbly cotri"` an elongatedbody, ah ampule'holde'r detachablylco ampule, aplunger Vslidablyl 4mountedwithin sa'ud and adapted for 'engagingandpropclling'affollowr1` inthe bore of said ampule to "dischargeliquidl sfr prope in 1d pairs within the body, each of said springscomprising a pair having different natural-frequencies, means forcompressing said springs, and means for suddenly releas ing thecompressed springs to perform propulsion Vof the plunger and follower.

2. In a hypodermic injector, an asembly comprising an elongated body, anampule holder detachably connected to one end thereof and adapted tohold an oriced ampule, a plunger assembly mounted within said bodycomprising a primary plunger and a sleeve-like secondary plungerslidably mounted on said primary plunger, the end of said primaryplunger being adapted to engage the central area of a llexible followerwithin the bore of said ampule and the end of said secondary plungerbeing adapted to engage the area surrounding said central area, powermeans including a tlanged sleevelike nut, a screw threadedly engaged inthe upper portion of said nut, and pairs of coil springs seated on saidnut, said primary plunger being threaded into the lower portion of saidnut and rotationally engageable with said screw to permit varying thedistance between the lower end of the primary plunger and said follower,and means for latching said screw against the compressive force of thesprings and for suddenly releasing the latch to propel said nut andplunger assembly.

3. The injector of claim 2 in which the latching means for the screwcomprises a pair of wedges adapted to support projections extending fromthe screw near the top end thereof, said wedges being radially slidablymounted in slots provided therefor in the body, and an axially movablerelease button of inverted cup shape mounted in the top of the bodyhaving an inwardly extending flange and a circumferential groove abovethe flange, said groove being adapted to receive said wedges when thebutton is depressed and said flange being adapted to force the wedgesfrom the groove and beneath said projections and prevent them frommoving outwardly when the button is in raised position.

4. In a hypodermic injector, an assembly comprising an elongated body,an ampule holder detachably connected to one end thereof and adapted tohold an orifced ampule, a plunger assembly mounted within said bodycomprising a primary plunger and a sleeve-like secondary plungerslidably mounted on said primary plunger, the end of said primaryplunger being adapted to engage the central area of a flexible followerwithin the bore of said ampule and the end of said secondary plungerbeing adapted to engage the area surrounding said central area, powermeans including a flanged sleeve-like nut, a screw threadedly engaged inthe upper portion of said nut, and pairs of coil springs seated on saidnu't, said primary plunger being threaded into the lower portion of saidnut and rotationally engageable with said screw to permit varying thedistance between the lower end of the primary plunger and said follower,the cooperating threads of said screw and said upper nut por- `tionhaving a faster lead than the cooperating threads of said primaryplunger and said lower nut portion, and

`means for latching said screw against the compressive cluding coilsprings disposed within diametrically opposed bores circumferentiallyspaced within the body, each bore containing two concentric springshaving the same natural frequencies as the corresponding springs in thebore diametrically opposed thereto, but different natural frequenciesfrom corresponding springs in adjacent bores. 6. In a hypodermicinjector, an assembly comprising Van elongated body, a cylindricalchamber in 'oneend thereof havinga bore terminating in 'a minute orificeand adapted to hold liquid' to be discharged from the injector,

.afollower within thevbore of said chamber, a plunger slidably mountedwithin said' body and adapted for engaging and propelling said followerto discharge liquid contents through said orifice, power means vforpropelling said plunger including coil springs mounted concentrically inpairs within the body, each of saidfsprings comprising a pair havingdifferent natural frequencies, means for compressing said springs, andmeans for suddenly releasing the compressed springs to performpropulsion ofthe plunger and follower;

Y References Cited inthe tile of this patent A UNITEDS'I`A'TES1:A'I`l1i`l'l`S Y smeer sept. 29, 1953 2,671,347 Scherer Mar.9, 1954

